UV assisted polymer modification and in situ exhaust cleaning

ABSTRACT

Methods and apparatus for the removal of exhaust gases are provided herein. In some embodiments, an exhaust apparatus may include a housing defining an inner volume; an inlet and an outlet formed in the housing to facilitate flow of an exhaust gas through the inner volume, wherein the inlet is configured to be coupled to a process chamber to receive an exhaust therefrom; and an ultraviolet light source to provide ultraviolet energy to the inner volume. The ultraviolet light source may provide sufficient energy to at least partially decompose the exhaust gases. In some embodiments, the ultraviolet light source may provide ultraviolet energy until the exhaust gas has cooled below a critical temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to semiconductorprocessing, and more particularly, to apparatus for removing exhaustgases from semiconductor process chambers.

2. Description of the Related Art

Many films used in electronic device fabrication are formed insemiconductor process chambers using process gases that may be reactedto form a desired layer on the substrate. The process gases that do notreact and gaseous byproducts formed during processing are then typicallyremoved through an exhaust system of the process chamber.

Unfortunately, unreacted process gases and process gas byproducts canpolymerize and/or condense on the surfaces of components of the exhaustsystem (e.g., within exhaust conduits). During continuous operation ofthe chamber, the polymerization and/or condensation of byproducts canresult in the constant, gradual formation of highly viscous liquids orsolids along the interior walls of the exhaust apparatus. As a result ofthis polymer build up, the exhaust apparatus can become at leastpartially blocked, reducing reactor exhaust flow efficiencies,increasing the possibility of substrate contamination, and generallyreducing overall chamber performance.

To address this problem, some exhaust apparatus may include exhausttreatment devices such as heaters or RF power sources for treating theexhaust gases to prevent or reduce polymer formation within the exhaustapparatus. Unfortunately, these methods have drawbacks as well. Forexample, apparatus which utilize heaters to react excess gases from theprocess chamber have temperature constraints (such as, about 500 degreesCelsius), which cause byproducts to still remain. Moreover, while theexhaust gases may not condense or polymerize where heated, thepolymerization may still occur downstream of the heater, once theexhaust gases start to cool. In addition, such systems do not work wellfor some processes. For example, such heating systems do not work wellwith reduced pressure deposition of polysilicon since polysiliconformation causes serious particle problems.

For reduced pressure polysilicon applications the exhaust gases may betreated with high frequency RF and nitrogen trifluoride (NF₃) tochemically etch the exhaust deposit. However, this methodology may raiseissues with fluorine contamination, materials compatibility, hazardouswaste disposal, and serious damage to the exhaust apparatus if not usedproperly.

Thus, there is a need in the art for improved methods and apparatus fortreating exhaust gases from semiconductor processes.

SUMMARY

Methods and apparatus for the removal of exhaust gases are providedherein. In some embodiments, an exhaust apparatus may include a housingdefining an inner volume; an inlet and an outlet formed in the housingto facilitate flow of an exhaust gas through the inner volume, whereinthe inlet is configured to be coupled to a process chamber to receive anexhaust therefrom; and an ultraviolet light source to provideultraviolet energy to the inner volume. The ultraviolet light source mayprovide sufficient energy to at least partially decompose the exhaustgases. In some embodiments, the ultraviolet light source may provideultraviolet energy until the exhaust gas has cooled below a criticaltemperature.

In some embodiments an apparatus for processing a substrate is provided.In some embodiments, an apparatus for processing a substrate may includea process chamber; and an exhaust apparatus coupled to the processchamber, the exhaust apparatus including a housing defining an innervolume; an inlet and an outlet formed in the housing to facilitate flowof an exhaust gas through the inner volume; and an ultraviolet lightsource to provide ultraviolet energy to the inner volume.

In some embodiments a method for removing an exhaust gas is provided. Insome embodiments, a method for removing an exhaust gas may includeproviding an exhaust gas to an exhaust apparatus; exposing the exhaustgas to an ultraviolet light source configured to provide sufficientenergy to at least partially decompose the exhaust gas; and removing theexposed exhaust gas from the exhaust apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 depicts a semiconductor processing chamber having an exhaustapparatus in accordance with some embodiments of the present invention.

FIG. 2 depicts a flow chart of a method for the removal of an exhaustgas in accordance with some embodiments of the present invention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale and may be simplifiedfor clarity. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Methods and apparatus for the removal of exhaust gases from asemiconductor process chamber are provided herein. In some embodiments,an exhaust apparatus having an ultraviolet (UV) light source isprovided. The UV light source may provide sufficient energy to exhaustgases in the exhaust apparatus to at least partially decompose theexhaust gases. The UV light source may advantageously preventpolymerization, self-polymerization, condensation, or the like, of theexhaust gases on the interior walls of the exhaust apparatus. The use ofa UV light source may be further advantageous for use in reducedpressure applications, wherein the exhaust gas is present in reducedconcentrations. In some embodiments, one or more supplemental gases maybe provided to the exhaust apparatus to react with the exhaust gases,thereby further limiting polymerization and/or condensation of theexhaust gases.

An apparatus for processing a semiconductor substrate in accordance withsome embodiments of the present invention is illustrated in FIG. 1. Theapparatus 100 includes a semiconductor process chamber 102, a gas supply110, a controller 112, and an exhaust apparatus 114. Althoughillustratively shown as coupled to an illustrative semiconductor processchamber 102 in FIG. 1, an exhaust apparatus in accordance with thepresent disclosure may be utilized in other suitable process chambers aswell. For example, the exhaust apparatus 114 may be coupled to processchambers such as those performing, e.g., epitaxial growth, reducedpressure epitaxial growth, chemical vapor deposition (CVD), or any othersemiconductor process chamber using processes requiring the removal ofexhaust gases that may undesirably condense or form polymers on theinterior of the exhaust system of the process chamber. One suchexemplary chamber that may benefit from the use of an exhaust apparatusas described herein is the RP EPI chamber available from AppliedMaterials, Inc. of Santa Clara, Calif.

The process chamber 102 may include a process chamber wall 103 at leastpartially defining a processing volume 104. A substrate support pedestal106 may be disposed in the process chamber 102 to support a substrate105 thereupon during processing. The substrate support pedestal 106 maybe any support pedestal for holding a semiconductor substrate and mayinclude such components as an electrostatic chuck, clamps, edge rings,guide pins, or the like for physically locating and retaining thesubstrate. The substrate support pedestal 106 may also includeadditional components for processing the substrate 105, such as anelectrode for supplying DC or RF bias power, systems for the uniformsupply or removal of heat from the substrate 105 or a surface of thesubstrate support pedestal 106, or the like.

The gas supply 110 may provide one or more suitable process gases forprocessing the substrate and/or for maintaining the process chamber 102(such as deposition gases, etch gases, cleaning gases, or the like). Thegas supply 110 may comprise a plurality of gas sources supplying one ormore process gases to the process chamber 102. Each process gas may besupplied independently, or in combination with additional process gases.Other components for controlling the flow of gases to the processchamber 102, such as flow controllers, valves, or the like, are, forsimplicity, not shown.

The gas supply 110 may provide process gases to the process chamber 102in any suitable manner, such as via a showerhead 108, gas distributionnozzles, inlets, or the like. The size, geometry, number, and locationof holes in the showerhead 108 can be selectively chosen to facilitate apredefined pattern of gas flow. The showerhead 108 depicted in FIG. 1 isexemplary and gases may enter the process chamber through other suitablemechanisms, such as nozzles, inlets, and/or fixtures in the chamberwall, proximate the substrate, or by any other suitable means forperforming the intended process in the process chamber 102. In someembodiments, the showerhead 108 may form at least part of an electrodefor supplying DC or RF power for the purposes of creating or maintaininga plasma from one or more of the process gases supplied by the gassupply 110. In some embodiments, the gas supply 110 may provide processgases to the process chamber 102 via side inlets. For example, someprocess chambers, such as those configured for epitaxial deposition ofsilicon may utilize a cross-flow gas distribution system wherein processgases a flowed across the surface of a substrate being processed.

The exhaust apparatus 114 may be coupled to the process chamber 102 viaan exhaust port 111. The exhaust apparatus 114 may be coupled to theprocess chamber 102 at any suitable location for exhausting the processchamber 102, such as along a sidewall of the chamber, as illustrated inFIG. 1. For example, depending upon chamber design and process gas flowconsiderations, the exhaust port 111 may be located at any suitablelocation in the process chamber 102, such as in a sidewall of theprocess chamber, above or below the surface of the substrate supportpedestal 106, in a floor of the process chamber, or in any othersuitable location.

The exhaust apparatus 114 generally includes a housing 118 defining aninner volume 120 and a UV light source 116 configured to provide UVenergy to exhaust gases present in the inner volume 120 of the housingduring use. The housing 118 may be of any desirable shape, volume, orcomposition commensurate with holding, flowing, or reacting the exhaustgases. It is contemplated that the shape, volume, and composition of thehousing 118 may depend on the identity of the exhaust gases, the desiredresidence time of exhaust gases flowing through the housing 118, or thelike. The housing 118 generally includes an inlet 122 for coupling tothe exhaust port 111 and an outlet 124 for coupling to an exhaust pump130.

The UV light source 116 may be any suitable UV light source havingsuitable intensity and wavelength required for providing energynecessary for at least partially decomposing an exhaust gas as describedherein. The UV light source 116 may be selected and/or operated toadvantageously provide this energy at a low temperature, therebyfacilitating cooling of the exhaust gases. An exemplary UV light source116 may be one of the Osram Xeradex® Systems, available from OsramSylvania Inc. of Danvers, Mass., such as the Xeradex® 20 lamp. Ofcourse, the particular UV source, number of sources, geometry, and thelike, may be configured as desired to provide the desired quantity of UVenergy to the exhaust gases present in the exhaust apparatus 114.

In some embodiments, the UV light source 116 may have a wavelength ofabout 124 nm or greater. In some embodiments, the UV light source 116may have a wavelength of about 172 nm or greater. However, the UV lightsource 116 may have any suitable wavelength and intensity necessary forat least partially decomposing an exhaust gas, preventing thepolymerization and/or self-polymerization, or preventing thecondensation of an exhaust gas can be used. In some embodiments, the UVlight source 116 may comprise a mercury (Hg) broadband UV light sourcefor providing UV light energy having a range of wavelengths.

The UV light source 116 may be disposed in a lamp housing 128. The lamphousing 128 may be vacuum sealed or may be purged with a suitable inertgas or gases. The lamp housing 128 may be coupled to the housing 118proximate a transparent window 126 for luminescently coupling to atleast a portion of the inner volume 120 of the housing 118. Thetransparent window 126 may comprise any suitable material, thickness,and/or geometry that facilitates illumination of the inner volume 120 bythe UV light source 116. The transparent window may be non-absorbing, orat most weakly absorbing in the wavelength range utilized by the lightsource 116. In some embodiments, the transparent window may comprisequartz.

The outlet 124 may be coupled to the vacuum pump 130 directly, or via aconduit 132, as illustrated in FIG. 1. In some embodiments, the outlet124 and the conduit 132 may be positioned in the housing 118 such thatlight from the UV light source 116 may travel at least partially downthe conduit 132. Although shown as being straight, the conduit 132 maybe curved, angled, or otherwise configured to couple the housing 118 tothe vacuum pump 130. In some embodiments, the conduit 132 may have atleast a straight portion 138 having a length at least as long asnecessary to allow the exhaust gases travelling therethrough to coolbelow a critical temperature at which the particular exhaust gasescondense, thereby advantageously minimizing polymerization that mayoccur downstream of the exhaust apparatus 114 (referred to herein as thecritical temperature). For example, when the exhaust gas comprisessilicon, such as when depositing silicon utilizing silicon hydride(SiH₂) as a precursor, the length of the straight portion 138 of theconduit 132 may be at least about 10 cm and/or up to about 100 cm. Ofcourse the desired length of the straight portion 138 of the conduit 132will depend many factors such as upon the flow rate, cooling rate, andor critical temperature of the exhaust gases utilized in a particularprocess.

In some embodiments, an interior surface of the conduit 132 may besufficiently smooth so as to minimize the turbulent flow of the exhaustgas flowing therethrough. Turbulent flow may undesirably promote mixing,reaction, and polymerization, or self-polymerization of the exhaust gas.In some embodiments, the interior surface of the gas outlet tube mayhave an root mean square (RMS) surface roughness of less than about 10Ra. In some embodiments, the interior surface of the gas outlet tube mayhave an root mean square (RMS) surface roughness of between about 5 Rato about 10 Ra. The length, diameter, geometry, interior surfaceroughness, and/or composition of the conduit 132 may be varied tofacilitate at least one of improved flow characteristics (e.g.,non-turbulent flow), increased cooling rates of the exhaust gas, or thelike.

In some embodiments, the exhaust apparatus 114 may further comprise asupplemental gas inlet 136 for supplying a supplemental gas from asupplemental gas source 140 to the inner volume 120. The supplementalgas may be any suitable gas that may be reacted with the exhaust gasesto prevent polymerization or to break down polymerized exhaust gases.The supplemental gas may be selected such that illumination thereof bythe UV light source 116 may form a reactive species for reacting withthe exhaust gases. In some embodiments the supplemental gas source 140may provide one or more etchant species, such as a halogen-containinggas, for example, hydrochloric acid (HCl), chlorine (Cl₂), fluorine(F₂), nitrogen trifluoride (NF₃), or the like. Alternatively or incombination the supplemental gas source 140 may provide one or moreoxidant species, such as an oxygen-containing gas, for example, oxygen(O₂), water (H₂O), or the like. Alternatively or in combination, one ormore of the above supplemental gases may be provided directly into theprocess chamber 102 (for example from the gas supply 110, or similar gassupply).

Upon being drawn through the exhaust apparatus 114 by the vacuum pump130, the exhaust gases may be expelled from the vacuum pump 130 into anexhaust system 134, as illustrated in FIG. 1. The exhaust system 134 mayinclude scrubbers, filtration units, or other forms of treatment and/orremediation devices for treating the exhaust gases prior to release intothe surrounding environment or prior to capturing the exhaust gases (orcomponents thereof) for further treatment, reuse, or disposal as may bedesired or required.

The controller 112 generally comprises a central processing unit (CPU),a memory, and support circuits and may be coupled to one or more of thecomponents of the apparatus 100 (or other controllers coupled thereto),and is generally capable of controlling any of the componentsindividually or in unison for performing a process within the chamber102. In operation, the controller 112 controls components and operationsof the apparatus 100, and/or provides instructions to controllersassociated with these components. In some embodiments, the controller112 is configured to cause the exhaust apparatus 114 to providesufficient energy via the UV light source 116 to at least partiallydecompose exhaust gases flowing through the exhaust apparatus 114 asdiscussed below with respect to FIG. 2.

In operation, the apparatus 100 may be utilized to process a substratewith reduced polymer formation/deposition within the exhaust system ofthe apparatus 100 by treatment of the exhaust gases with the exhaustapparatus 114. For example, inventive methods for the removal of exhaustgases in accordance with some embodiments of the present invention aredepicted in FIG. 2, and described below with respect to the apparatus100.

The method 200 generally begins at 202 where exhaust gases from theprocess chamber 102 are provided to the exhaust apparatus 114. Theexhaust gases may comprise at least one of excess and/or unreactedprocess gases (e.g., from the processing of a substrate), process gasbyproducts and/or processing byproducts (e.g., formed by a reaction thatoccurs in the processing volume 104 between at least one or more processgases or between the substrate 105 and one or more process gases), orthe like, and will vary depending upon the process being performed inthe process chamber 102. In some embodiments, the exhaust gases maycomprise one or more of silicon, hydrogen, or a halogen. For example, insome embodiments, the exhaust gas may include at least one siliconspecies, such as at least one of silicon hydride radicals (SiH₂), silane(SiH₄), disilane (Si₂H₆), dichlorosilane (SiH₂Cl₂), trichlorosilane(SiHCl₃), or other higher order silicon and hydrogen containing gases,or the like. Alternatively or in combination, in some embodiments, theexhaust gas may include at least one germanium species, such as germane(GeH₄), or the like.

The exhaust gases enter the inner volume 120 of the exhaust gasapparatus 114 at the inlet 122 via the exhaust port 111. The exhaustgases may be of sufficient temperature to be reactive by polymerizationand/or self-polymerization (referred to herein simply aspolymerization). Herein, polymerization is understood to mean apolymerizing reaction between exhaust gases having different chemicalcompositions, and self-polymerization is understood to mean apolymerizing reaction between exhaust gases having the same chemicalcomposition. The polymerization and self-polymerization may result incondensation of a polymerized product of one or more exhaust gases onthe interior surfaces of the exhaust apparatus 114. In some embodiments,the temperature of the exhaust gases may be greater than a criticaltemperature (for example, in some embodiments, greater than about 100degrees Celsius) and may cool as it travels through the exhaustapparatus 114 (and/or through the pump 130 and exhaust system 134).

Next, at 204, the exhaust gases in the exhaust apparatus 114 are exposedto light energy from the UV light source 116. The UV light source 116provides sufficient energy to at least partially decompose the exhaustgas, thereby breaking down longer polymer chains that may condense ontothe surfaces of the exhaust apparatus 114. In some embodiments, the UVlight source 116 may provide energy sufficient to decompose the exhaustgases until the exhaust gases cool below a critical temperature at whichthe exhaust gases no longer polymerize. For example, in some embodimentswhere silicon, hydrogen, and chlorine are present, the criticaltemperature may be between about 100 degrees to about 250 degreesCelsius. In some embodiments, the UV light source 116 is configured toprovide energy to the exhaust gases present in the inner volume 120 andat least up to a length of the straight portion 138 of the conduit 132beyond which the exhaust gases have cooled to below the criticaltemperature.

Exposure to the UV light source may advantageously reduce polymerizationof the exhaust gases within the exhaust apparatus 114, pump 130 and/orthe exhaust system 134 of the apparatus 100. Moreover, the UV lightsource may advantageously reduce polymerization of the exhaust gaseswhile allowing the exhaust gases to cool to below the criticaltemperature at which polymerization no longer occurs, thereby avoidingpushing polymerization reactions downstream of the exhaust apparatus andadvantageously reducing polymer formation in other portions of theapparatus 100 (such as the pump 130 and/or the exhaust system 134).

The wavelength of energy provided by the UV light source 116 may beselected based upon the exhaust gases being processed. For example, insome embodiments, wherein the exhaust gases include chlorine (Cl₂),energy may provided by the UV light source 116 at a wavelength of about124 nm. In some embodiments, wherein the exhaust gases includehydrochloric acid (HCl), energy may be provided by the UV light source116 at a wavelength of about 172 nm. The intensity of the UV lightsource 116 may also be adjusted as necessary, for example, based uponthe concentration of the exhaust gases provided to the exhaust apparatus114. For instance, a reduced concentration of the exhaust gases mayrequire reduced intensity from the light source 116 for a reaction tooccur.

In some embodiments, for example wherein the exhaust gases substantiallycomprise non-halogen containing gases, one or more supplemental gasesmay be provided into the exhaust apparatus 114 along with the exhaustgases, for example, from the supplemental gas source 140 via thesupplemental gas inlet 136 (as shown in FIG. 2 in phantom at 206). Thesupplemental gas may comprise an etchant and/or an oxidant gas, such asone or more of the supplemental gases discussed above. The supplementalgas (when present) may be at least partially decomposed by energyprovided by the UV light source 116, thereby forming a reactive specieswhich may react with the exhaust gases to form a volatile byproduct thatdoes not polymerize.

Thus, the inventive exhaust apparatus 114 may be utilized in connectionwith processes that utilized gases that may otherwise form polymers andcondense on the walls of the exhaust systems of the process chamber. Forexample, exhaust gases such as SiH₂ radicals and Cl₂, which may beutilized in chemical vapor deposition of silicon-containing films, mayreact to form SiCl₄ and Si_(x)H_(y)Cl_(z), wherein x, y, and z areintegers greater than 1. The Si_(x)H_(y)Cl_(z) may form long polymerchains and would typically deposit or condense onto the surface of theexhaust systems of the process chamber. Using the inventive exhaustapparatus 114, the exhaust gases may be provided with energy by the UVlight source 116, thereby breaking down the long chains ofSi_(x)H_(y)Cl_(z) into shorter, more volatile chains, and furtherpreventing the formation of Si_(x)H_(y)Cl_(z) in the exhaust apparatus114. Moreover, the exhaust apparatus 114 further allows the exhaustgases to cool to below the critical temperature while breaking down theexhaust gases, thereby allowing the exhaust gases to by removed from theexhaust apparatus 114 and pumped away without further downstreamcontamination of the exhaust systems.

Upon completion of 204, the method 200 ends and the exhaust gases areremoved from the exhaust apparatus 114 and pumped into the exhaustsystem 134 by the pump 130, wherein the exhaust gases may be exhausted,treated, stored, or otherwise processed as necessary.

Thus, methods and apparatus for the removal of exhaust gases fromprocess chambers has been provided herein. The inventive methods andapparatus utilize UV light energy provided by a UV light source to atleast partially decompose exhaust gases and/or to react the exhaustgases to form byproduct gases with improved volatility and/or lessreactivity at operating temperatures, thereby reducing polymerizationand condensation on the interior walls of the exhaust apparatus.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A method for removing an exhaust gas, comprising:flowing an exhaust gas from a semiconductor process chamber through anexhaust apparatus coupled to the semiconductor process chamber, whereinthe exhaust gas flows through an inner volume of the exhaust apparatussubstantially free from obstruction; exposing the exhaust gas within theexhaust apparatus to an ultraviolet light source to at least partiallydecompose the exhaust gas as it flows through the exhaust apparatus;exposing the exhaust gas to a supplemental gas comprising ahalogen-containing gas; and flowing the at least partially decomposedexhaust gas from the exhaust apparatus.
 2. The method of claim 1,wherein the exhaust gas comprises at least one of silicon hydrideradicals (SiH₂), silane (SiH₄), disilane (Si₂H₆), dichlorosilane(SiH₂Cl₂), trichlorosilane (SiHCl₃), or germane (GeH₄).
 3. The method ofclaim 1, wherein the supplemental gas comprises at least one ofhydrochloric acid (HCl), chlorine (Cl₂), fluorine (F₂), or nitrogentrifluoride (NF₃), and optionally further comprises at least one ofoxygen (O₂) or water vapor (H₂O).
 4. The method of claim 1, wherein theultraviolet light source provides ultraviolet energy to the supplementalgas to create a reactive species.
 5. The method of claim 1, wherein theultraviolet light source provides energy to the exhaust gas until theexhaust gas cools to a critical temperature at which the exhaust gascondenses.
 6. The method of claim 5, wherein the critical temperature isless than about 250 degrees Celsius.
 7. The method of claim 1, whereinthe ultraviolet light source has a wavelength of about 124 nm orgreater.
 8. The method of claim 1, wherein the ultraviolet light sourcehas a wavelength of about 172 nm.
 9. A method for removing an exhaustgas, comprising: flowing an exhaust gas from a semiconductor processchamber through an exhaust apparatus coupled to the semiconductorprocess chamber, wherein the exhaust gas flows through an inner volumeof the exhaust apparatus substantially free from obstruction; exposingthe exhaust gas within the exhaust apparatus to an ultraviolet lightsource to at least partially decompose the exhaust gas as it flowsthrough the exhaust apparatus, wherein the ultraviolet light sourceprovides energy to the exhaust gas until the exhaust gas cools to acritical temperature at which the exhaust gas condenses; and flowing theat least partially decomposed exhaust gas from the exhaust apparatus.10. The method of claim 9, wherein the critical temperature is less thanabout 250 degrees Celsius.